The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a method for forming a fine pattern in a semiconductor device.
Amorphous carbon has been used as part of a hard mask stack structure for use in patterning an N-channel metal-oxide semiconductor field effect transistor (NMOSFET) device when forming a fine pattern of 100 nm or less. Such a technology allows easier patterning, and exhibits better selectivity than typical capping or protective materials of a silicon oxide (SiO2) layer, silicon nitride (Si3N4) layer, and a silicon oxynitride (SiON) layer.
However, using amorphous carbon as a hard mask increases fabrication costs up to ten times when compared to using a polysilicon layer as the hard mask. Furthermore, amorphous carbon exhibits deteriorated step coverage when formed over a peripheral region with large height differences, i.e., over various key boxes (e.g. align keys) used for monitoring photo and etch processes. Thus, a subsequent SiON layer may be formed unevenly. Consequently, when performing a rework process on photoresist during a photo-exposure process, portions of the amorphous carbon may be lost. Furthermore, undesired consequences, such as lifting and particle generation, may occur on the device where the portions of the amorphous carbon are lost.